1. Field of the Invention
The invention relates to a method for operating a multiphase line, which is included in a transmission network, for the transmission of electrical power, and to an apparatus for carrying out this method.
2. Discussion of Background
When faults occur in a line in an electrical transmission network, attempts are normally made to overcome the fault in the line by quickly switching on again. However, if this process of quickly switching on again is unsuccessful, then all three phases of the relevant line must be switched off until the fault has been rectified. The relevant line cannot be used throughout this switched-off period. If this switched-off line is used as a link between two important nodes in the transmission network, then this interruption can cause problems in network operation; it may, for example, have a negative influence on the stability of the network, or it may lead to thermal overloading of lines that are still in the network.
The use of three-point invertors in transmission networks is known, for example, from the article "Analysis of a 3-level-VSI neutral-point-control for fundamental frequency modulated SVC-applications", which was introduced at the IEE Meeting on April 29-May 3 1996 and was published as Conference Publication No. 423, pages 303 to 310.